Not only did the freshman senator face a challenger with an unusual financial advantage, he also beat back what Republicans had hoped would be a decisive issue in Pennsylvania and other coal states across the nation: that President Obama and the Democrats were waging a war on coal that hurt jobs and the economy.

"While we came up a little big short tonight, let me tell you it remains the same: We must repeal Obamacare. We must stop deficit spending. We must end this war on American energy, this war on Pennsylvania coal. And most importantly, we must get this economy roaring again," Mr. Smith said in his concession speech Tuesday night.

With a war chest of some $20.3 million, Smith mounted an aggressive television ad campaign that dubbed Senator Casey as "the invisible senator," who hadn't passed a single bill in six years, "even to help jobs." A newcomer to politics, Smith brought the race to within single digits, but was never able to overcome the incumbency advantage and Casey's popularity in the state.